Phase control arrangements for a multiport system



J. L. BUTLER Sept. 27, 1966 PHASE CONTROL ARRANGEMENTS FOR A MULTIPORTSYSTEM 5 Sheets-Sheet 1 Filed May 8, 1963 Sept. 27, 1966 J. L. BUTLER3,276,018

PHASE CONTROL ARRANGEMENTS FOR A MULTIPORT SYSTEM Filed May 8, 1963 5Sheets-Sheet 2 J. L. BUTLER Sept. 27, 1966 PHASE CONTROL ARRANGEMENTSFOR A MULTIPORT SYSTEM Filed May 8, 1963 5 Sheets-Sheet 3 J. L. BUTLER3,276,018

PHASE CONTROL ARRANGEMENTS FOR A MULTIPORT SYSTEM Sept. 27, 1966 5Sheets-Sheet 4 Filed May 8, 1963 J. L. BUTLER Sept. 27, 1966 5Sheets-Sheet 5 Filed May 8, 1963 United States Patent 3,276,018 PHASECONTROL ARRANGEMENTS FOR A MULTIPQRT SYSTEM Jesse L. Butler, GrotonRoad, RFD. 2, Nashua, NB. Filed May 8, 1963, Ser. No. 278,854

17 Claims. ((11. 343-100) This invention relates to phase controlarrangements and more particularly to phase control arrangementsparticularly useful in the control of directional properties of antennaarrays of-the type used in a radar system, for

example. 7 V

The directional characteristics of certain antenna arrays are a functionof the relative phases of the signals applied to the individual antennaelements of the array wherein a uniform phase gradient is providedacross the aperture of the array. Stable but adjustable phase shiftcomponents are required for accurately controlling this phase gradient.One method of varying the directional characteristics of such an arraywould be to employ a group of variable phase shifters which arecoordinately controlled. However, variable phase shifters having rapidresponse (which in general requires no moving parts) and accuratelypredictable phase control characteristics are very difficult to achieve,particularly the ultra high and microwave frequencies employed in radarsystems. A1- ternative proposals suggest the use of fixed phase shiftersand control arrangements to selectively connect the phase shifters inthe energized circuit to provide the several different desired phasegradients, each of which produces a beam with different directivitycharacteristics. As the phase of each signal applied to an array elementmust be varied as a function of the phase of the signal applied to theadjacent elements in order to change the phase gradient whilemaintaining a uniform phase difference between adjacent antennaelements, these proposals have required the use of astronomicalquantities of control hardware. In particularly sophisticated antennasystems which produce a very narrow beam and consequently employ a greatnumber of radiating elements and have a multitude of beam positions tobe covered, such arrangements appear to be economically unfeasible.

Accordingly, it is an object of this invention to provide a novel andimproved antenna array beam control system.

Another object of the invention is to provide a novel and improvedcontrol system for an antenna system of the phased array type whichenables accurate and rapid phase gradient switching to control thedirectivity characteristics of the antenna system.

Another object of the invention is to provide a new and improvedelectronic beam forming and steering antenna system.

Still another object of the invention is to provide a novel and improvedphase control system that is more economical to manufacture and use thanphase control systems of this type that have been heretofore proposed.

A further object of the invention is to provide a novel and improvedphase control system that is particularly susceptible to digitalcontrol.

This invention provides a digitally controlled phase shifting systemwhich employs a plurality of fixed phase shifters with phase shifterisolating means associated with each phase shifter to control thetransfer of energy to or from a plurality of array elements (energycoupling ports). While the invention has particular use in antennaarrays, its use is not limited thereto, and it may be used, for example,in frequency analysis where the array elements are coupling elementsspaced along a delay line. The phase shifters are arranged in modules,each module including a plurality of phase shifters corresponding innumber to the radix of digital control employed. For example,

where the digital control information is in binary radix each phasemodule includes two phase shifters. The modules in a level of controlcorresponding to an order of the digital control word are arranged sothat the phase shifter of one module imparts a phase shift radiansdifferent from the corresponding phase shifter in the immediatelyadjacent module and the other phase shifters in that module impart phaseshifts K radians different from the corresponding phase shifters in theimmediately adjacent module. A phase shifter of each module is connectedin circuit as selected by digital control information and the modulematrix distributes the energy so that a uniform phase difference betweenthe array elements is produced. This controlled phase gradientcharacteristic enables a beam with the desired directivitycharacteristics to be produced at an antenna array for example.

Numerous array configurations are possible through phase module, powerdivider combinations. In certain embodiments of the invention combinedpower dividerphase shifting devices are employed in conjunction withphase module arrangements to produce the digitally controllable ph asegradient characteristics of the antenna array. Further, the illuminationof the array aperture may be uniform or tapered, as a cosinedistribution, as desired. The invention provides precise control ofphase gradient characteristics of an antenna array in response todigital control signals, and enables the generation of and rapidswitching between a plurality of different beams of accurate directivitycharacteristics with a substantial reduction in the cost and complexityof the required control components.

Further objects, features and advantages of the invention will be seenas the following description of embodiments thereof progresses, inconjunction with the drawings, in which:

FIG. 1 is a diagrammatic illustration of a phased array antenna beamcontrolling matrix constructed in accordance with the invention;

FIG. 2 is a diagram of a larger phase control matrix of the same type asshown in FIG. 1;

FIG. 3 is a diagrammatic illustration of the several beam positions thatmay be generated with the antenna array as controlled by the matrixshown in FIG. 2;

FIGS. 4 and 5 are diagrams of phase control matrices which feed four andfive antenna elements respectively;

FIG. 6 is a diagram of a modified ph ase control matrix constructed inaccordance with the invention which employs two legged and three leggedphase modules;

FIGS. 7A and B are diagrams of sitll another embodiment of a phasecontrol matrix constructed in accordance with the invention which employphase module arrangements that include hybrid couplers; and

FIG. 8 is a diagram of a phased antenna array control matrix whichprovides a cosine distribution array aperture illumination.

The antenna array shown in FIG. 1 has four antenna elements 1-4 whichare energized from a source 10 through a phase control matrix so thatradiated beams of four different directional characteristics may beproduced. The matrix comprises six similar phase control modules 12,each of which includes two fixed phase shifters 14, 16 and four controlswitches 18, 20, 22, 24. When control switches 18 and 24 are energized,phase shifter 14 is connected in the circuit and when switches 20 and 22are energized, phase shifter 16 is connected in circuit.

The energization of the control switches is in response to digitalcontrol information from source 30, which has four output lines 32, 34,36, 38. Lines 32 and 34 represent the zero and one values of the lowestorder of digital control information and lines 36 and 38 represent thezero and one levels of the next more significant order of digitalcontrol information. For example, when line 32 is energized, indicatingthe value of the lowest order of digital control information is zero,control switches 18 land 24 are conditioned to connected phase shifter14 in the circuit to antenna element 1. At the same time the leftbranches of the other three modules 40, 42, 44 in the upper level arealso conditioned to connect the phase shifter in the left branch of eachmodule to the antenna elements 2, 3 and 4 respectively. Should line 34be energized, control switches 20 and 22 would be conditioned andconnect phase shifter 16 in circuit with antenna element 1 andcorrespondingly the phase shifters in the right branches of the modules40, 42, 44 in the upper level Would be connected to the antennaelements. Only one line 32 or 34 is energized at any one time so thatunambiguous control is provided.

A similar control over the two phase shifters 46, 48 of the second levelare provided by signals on lines 36 and 38. A signal on line 36conditions the switches to connect the phase shifters in the leftbranches of the phase modules 46, 48 in circuit, and a signal on line 38conditions corresponding switches to connect the phase shifters in theright branch of the phase modules in circuit.

The source is connected to the inputs of phase modules 46 and 48 througha power divider 50. The output of phase module 46 is connected to theinputs of phase modules 12 and 42 through a power divider 52 and theoutput of phase module 48 is connected to the inputs of phase modules 40and 44 through a power divider 54. These power dividers 50, 52 and 54split the power applied on the input equally to the two output branches.Thus power from a source connected at terminal 10 is divided forapplication to the antenna elements 1, 2, 3 and 4 equally.

The phase shift imparted to the power transmitted from terminal 10 tothe antenna elements is indicated .in the following table:

TABLE I Antenna Elements Digital Control Phase Difierential (M) 1 2 3 4mwoao own- 01 mum-no It will be noted that there is uniform phasegradient (Aqfi) imparted across the four antenna elements imparted bythe phase control matrix. For the digital control value 00, a phasegradient of 3 units is imparted (each unit being in terms of 1r/4radians). For the digital control signal 01 a phase gradient of 1 unitis imparted; for the digital control signal 10, a phase gradient of +1unit is imparted; and for the signal 11 a phase gradient of +3 units isimparted.

An extension or enlarged antenna array of similar configuration is shownin FIG. 2. This array has eight antennas 61-68 which may be energizedfrom a source 70 through a three level phase control matrix to producebeam of directional characteristics of the type indicated in FIG. 3. Thephase control matrix employs a plurality of phase control modules of thesame type as those employed in the arrangement of FIG. 1. Each includestwo phase shifters 'and four control switches which are adapted toisolate one or the other phase shifter from an energy transmission pathdepending on the nature of the binary control signal applied thereto. Asin the case of FIG. 1, the phase shift introduced by each phase shifterin the matrix is indicated on the corresponding phase shifter symbol, inthis case in terms of 1r/8 radians. For example, the phase shifter 72 inthe left leg of module 4 74 introduces a phase shift of 41r/ 8 radiansor 90", while the phase shifter 76 in the right leg of that moduleintroduces a phase shift of 0.

The phase shifter matrix shown in FIG. 2 has three control leveis 80, 82and 84, each level corresponding to an order of the digital control wordthat is to be employed to select the phase shifters for connection incircuit. One phase shifter in each module is connected in circuit inaccordance with binary information. Thus phase shifter 72 is connectedin circuit of the binary control signal at level is zero and phaseshifter 76 is connected in circuit if the control signal at level 80 isOne-3,

It will be noted that the phase shifter arrangement in the matrix, aswas the case in FIG. 1, is symmetrical and that the phase shifters arearranged in identical series on either side of the center. At level 80either a shift of O or (iv/2) is introduced; at level 82 45 increments(1r/4) are employed; and at level 84 the phase shifters aresymmetrically arranged in 22.5 increments (1r/ 8). The phase shiftincrements at level 84 increase outwardly from the center to the outsidephase shift module on the zero legs and then continue to increase fromthe outside module back to the center module on the one legs. A similarsymmetry is employed in levels 80 and 82. This symmetry is consistentwith the fixed phase difference of corresponding branches or legs ofadjacent modules. Thus the zero legs at level 84 differ by 1r/8 radiansand the one legs differ by +1r/8 radians. Similarly, the zero legs atlevel 32 differ by -11-/4 radians and the one legs by +1r/4 radians,while the zero legs at level 80 differ by 1r/2 radians and the one legsby +1r/2 radians.

Each phase module is connected to the next module through a powerdivider 86. In the matrix of FIG. 2 all the power dividers are of equalvalue-splitting the power applied on input leg 87 equally to each outputleg 88, 89. This matrix thus supplies equal power to all of the antennaelements 6168.

The phase shift introduced to the signal from terminal 70 by thebranching matrix for application to the antenna elements 6168 isindicated in the following Table II as a function of the binary controlsignals applied to the levels of the matrix.

TABLE II Digital Antenna Elements Control Beam 11 (Fig. 3) 80 82 84 6162 63 64 65 66 67 68 0 O O 9 2 11 4 13 6 15 8 -7 4L 0 0 1 10 5 16 11 6 112 7 5 3L 0 1 0 11 8 5 2 15 12 9 6 3 2L 0 1 1 12 11 10 9 8 7 6 5 1 1L 10 0 5 6 7 8 9 10 11 12 +1 1R 1 0 1 6 9 12 15 2 5 8 11 +3 2R 1 1 0 7 12 16 11 16 5 10 +5 3R 1 1 1 8 15 6 13 4 11 2 9 +7 4R From this table itwill be observed that when all three binary control signals are zero(000-) the phase differential applied to the antenna elements is 71r/ 8which produces a beam position denominated 4L in FIG. 3. When thedigital control signal is changed to 00 1 the phase differential at theradiating elements is changed to 51r/ 8 producing the radiated beamdenominated 3L in FIG. 3. The other beams indicated in the table maysimilarly be correlated with FIG. 3.

The phase differences that are applied to the antenna elements may bedetermined directly from FIG. 2. For example, when the input digitalcontrol signal is 000, antenna element 64 has a signal applied to itthrough a 0 phase shift at level 80, a 90 phase shift at level 82 and aphase shift at level 84 producing a total phase shift of 90 or 45/8radians. On the same antenna element when the input signal is 111 thephase shift introduced at level 80 is 90", at level 82 is 45 and atlevel 84 is 157.5-a total of 292.5 (l31r/8 radians). While the aboveanalysis is stated in terms of a signal being applied at a supplyterminal to the modules, the components of an incoming wave front whichproduces the indicated phase gradient at the modules will be combined insimilar manner at terminal 70. Thus these control matrices providesdigitally controlled phase differentials with resulting beam directivitycharacteristics. The number of beam positions are a function of thedigital control signals.

The number of antenna elements may be varied as indicated in FIGS. 4 andwhich are, illustrative of a radiating matrix producing eight beampositions (three binary levels )as does the matrix of FIG. 2. Table IIIwhich is similar to Table I but refers to FIG. 4 indicates the phaseshift for an array having four antenna elements 91-94 which produceseight beam positions.

6 Again, a symmetry is employed in which the module leg phasedifferences at level 124 are 4 units; at level 126 :2 units; and atlevel 128 :1 unit.

In FIG. 6 there is shown a phase shifting arrangement in which threethree-legged phase modules 140, 141, 142 are employed at level 144 incombination with a set of two-legged phase modules at level 146. Againas in the above examples, this phase matrix employs a symmetricalarrangement with the connections between levels interlaced so that eachmodule in the lower level 144 is connected to the two correspondingmodules in the upper level 146. In the level 146 six two-legged phaseshift modules 148-153 are symmetrically arranged with :Ll unit phasedifferences between corresponding legs of adjacent modules (in terms ofTF/ 6 radians). In the level 144 the phase difference between the zerolegs is two units; between the one legs is six units; and between thetwo legs is ten (or minus two) units. The six antenna elements 161-166receive equal energy in this embodiment. This matrix produces sixdifferent beam positions at the six antennas as indicated in thefollowing table:

TABLE III TABLE v Elements Antenna Digital A Control Digital AntennaElements 91 92 93 94 Control 0 0 0 9 2 11 4 7 114 l 146 101 1G2 103 151165 106 0 0 1 6 1 12 7 5 0 1 0 11 s 5 2 -3 0 1 1 s 7 6 5 -1 0 0 2 3 4 5s 7 +1 1 0 0 5 6 7 8 +1 0 1 3 6 9 0 3 6 +3 1 0 1 2 5 8 11 +3 1 0 2 7 0 510 3 +5 1 1 0 7 12 1 6 +5 1 1 3 10 5 0 7 2 +7 1 1 1 4 11 2 9 +7 36 2 0 e3 0 9 6 3 +9 2 1 7 6 5 4 3 2 +11 In this arrangement, as in thearrangement shown in FIG. 1, power splitters having outputs of equalvalue are em- 40 ployed. Levels and 96 have phase shift modules arrangedin the same manner as levels 80 and 82 in the matrix of FIG. 2. Level97, however, has a modified arrangement3-0, 2-1, 1-2, 0-3, which, itwill be noted, is symmetrical with a fixed difference betweencorresponding legs of the modules of i1 units. Other :1 unit moduledifferences can also be employed-for example, 3-4, 2-5, l-6, 0-7, whichis obtained by eliminating antenna elements 65-68 from the matrix ofFIG. 2.

Where a different number of antennas are employed, however, powerdividers of different values may be utilized as shown in FIG. 5. In thiscase the power divider 100 applies /5 of the power on line 102 and /s ofthe power on line 104. Power divider 106 splits the power /3 on line 108and /3 on line 110. An equal power split is provided by divider 112, /2to each of lines 114 and 116. The power divider 118 also supplies /2power to line 120 and /2 to line 122. Thus this arrangement suppliesequal power to the five antenna elements. The phase gradient acrossthese antenna elements for the digital control signals is indicated inthe following table:

As indicated in the table, equal phase gradients are produced by thevarious combinations of control signals applied to the phase modules. Byappropriately combining modules in this manner a wide variety of phaseshift increments between adjacent antenna elements may be obtained.

Still another arrangement is illustrated in FIGS. 7A and B in which asymmetrical arrangement of phase shift modules are interlaced withhybrid couplers (three db directional couplers) and single pole-doublethrow switches. In this arrangement eight phase shift modules arereplaced by seven hybrid couplers (with a slight additional modificationin the nature of the phase modules) to produce a scanning systemequivalent to that shown in FIG. 2. In this arrangement eight antennaelements 201-208 are arranged in two sections. The corresponding arrayelements in each section are fed from the same hybrid. For example,elements 201 and 205 are fed from the output ports of hybrid 210.Similarly, elements 202 and 206 are fed from the output ports of hybrid212.

The input ports of each hybrid are connected to a phase shift module 220which has two fixed phase shifters 222, 224 of phase shift values asindicated which are fed by a digitally controlled single pole-doublethrow switch 226. The corresponding modules in the two sections at level228 are fed from the output ports of hybrids 230, 232 and the inputports of those hybrids are connected to phase modules 240, 242. Thesetwo phase modules are connected to the output ports of hybrid 248 andthe input ports of that hybrid are connected through single poledoublethrow switch 250 to terminal 252. The phase shifts imparted by thismatrix are indicated in FIG. 7B and the several phase differentials forthis matrix, which are a function of the position of the digitallycontrolled switches, are indicated in the following table:

TABLE VI Antenna Elements Digital Control mp 0 0 6 7 8 9 11 12 +1 0 0 16 9 12 2 5 8 11 +3 0 l 0 7 12 1 6 11 16 5 10 +5 0 l 1 8 15 6 13 4 11 2 9+7 1 0 0 9 2 11 4 13 6 l5 8 +9 (-7) 1 0 1 10 5 16 11 6 1 12 7 +11 (5) l1 0 11 8 5 2 15 12 9 6 +13 (3) 1 l 1 12 11 10 9 8 7 6 5 +15 (l) Alimitation on the use of this arrangement is that the hybrid couplersmust give equal power division and hence the energy distribution at thearray aperture must be uniform in amplitude. Tapered aperturedistributions are often preferred in order to reduce the side lobes ofthe array pattern. A modified arrangement of the hybrid coupler-phasemodule arrangement is shown in FIG. 8 which enables a cosinedistribution to be obtained. In this arrangement two sets of controlmatrices 260, 262 are employed which are digital programmed separately,and their outputs are applied to a combined phase module hybrid circuit264 for application to the array elements 266. By the separateprogramming of two sets of control matrices 260, 262 the resultingaperture distribution may be caused to be the sum of two uniform linearamplitude distributions which have incremental phase differences thatdiffer by the function 21r/K.

Where the switches are set as shown in solid lines, the left handnetwork 260 produces a phase differential between adjacent antennaelements of 1r/ 16 and the right hand network 262 produces an elementphase differential of 31r/16. The resulting distribution on the arrayhas a phase differential of 1r/ 8 with a cosine amplitude distribution.If the A switches in the left hand control section are changed to thedashed position, the left hand network 262 is set for a distributionwith a phase differential of 51r/ 16 to produce a total phasedifferential across the elements of the array of 1r/ 8. Again the resultamplitude distribution is cosine in nature in which the amplitude of theexcitation on the center elements of the array is the greatest anddecreases outwardly in accordance with the relationship cos (XL/2) whereX is the distance of the element from the center of the array and L isthe length of the array.

While preferred embodiments of the invention have been shown anddescribed, various modifications thereof will be apparent to thoseskilled in the art and therefore it is not intended that the inventionbe limited to the disclosed embodiment or to details thereof anddepartures may be made therefrom within the spirit and scope of theinvention as defined in the claims.

I claim:

1. Phase control apparatus for a system having a plurality of energycoupling ports,

said system being responsive to digital control words,

comprising a multiplicity of phase control modules arranged in aplurality of levels in a matrix,

each said phase control module in each level having N branches where Nis the radix of said digital control word applied to that level,

each said branch including a phase shifter which imparts a fixed andpredetermined amount of phase shift to a signal applied to that branchand selection means for connecting that branch in circuit,

each said level corresponding to an order of said digital control word,

power divider means for connecting the modules in one level to themodules in the succeeding level.

and means to actuate said phase shifter selection means in accordancewith the digital control words to connect each said port through a phasemodule in each level so that said matrix produces a correspondinguniform phase differential between said ports in said system.

2. The phase control apparatus as claimed in claim 1 wherein each levelincludes N times as many phase modules as the preceding level where N isthe radix of the digital control of that level.

3. The phase control apparatus as claimed in claim 1 wherein each saidselection means includes two phase shifter isolating devices,

one disposed on either side of the phase shifter connected in the branchcontrolled by the selection means.

4. The phase control apparatus as claimed in claim 1 wherein saiddigital control words are in the binary radix and each said phasecontrol module further includes a hybrid coupler connected to the twophase shifters in each module.

5. Phase control apparatus for a system having a plurality of energycoupling ports,

said system being responsive to binary control words,

comprising a multiplicity of phase control modules arranged in aplurality of levels in a matrix,

each said level corresponding to an order of said binary control word,

power divider means for connecting the modules in one level to themodules in the succeeding level,

each said phase control module in each level having two branches,

each said branch including a phase shifter which imparts a fixed andpredetermined amount of phase shift to a signal applied to that branchand selection means for connecting that branch in circuit,

the phase shifter in one branch of each module imparting a shift 5radians different from the phase shifter in the corresponding branch ofthe immediately adjacent module in the same level and the phase shifterin the other branch of each module imparting a shift K radians differentfrom the phase shifter in the corresponding branch of said immediatelyadjacent module, where K is an integer,

and means to actuate said phase shifter selection means in accordancewith the binary control words to connect each said port through a phasemodule in each level so that said matrix produces a correspondinguniform phase differential between said ports in said system.

6. The apparatus as claimed in claim 5 wherein said power divider meansincludes a four port coupler associated with each module, said couplerhaving two input ports and two output ports,

means connecting each input port to a corresponding phase shifter in theassociated module and means connecting each output port to a phasemodule in the succeeding level.

7. The apparatus as claimed in claim 6 wherein said selection meansincludes a single pole-double throw switch device 'for connecting one ofsaid phase shifters in each module in circuit in response to the binarycontrol signal applied to that level.

8. Phase control apparatus for a system having a plurality of ports,

said apparatus being responsive to digital control words,

ham.

comprising a plurality of phase control modules arranged in a levelcorresponding to an order of said digital control words,

each said phase control module having N branches where N is the radix ofsaid digital control words,

each said branch including a phase shifter which imparts a fixed andpredetermined amount of phase shift to a signal applied to that branchand selection means for connecting that branch in circuit, the phaseshifter in one branch of each module imparting a shift radians differentfrom the phase shifter in the corresponding branch of the immediatelyadjacent module and the phase shifter in another branch of each moduleimparting a shift g radians different from the phase shifter in thecorresponding branch of said immediately adjacent module, the shiftsimparted by the phase shifters in said one branches of the modules beingin inverse relation to the phase shifts imparted by the phase shiftersin said another branches of the modules,

and means to actuate said phase shifter selection means in accordancewith the digital control words to connect each module so that saidapparatus produces a uniform phase differential between said ports insaid system.

9. The phase control apparatus as claimed in claim 8 wherein each saidselection means includes two phase shifter isolating devices, onedisposed on either side of the phase shifter connected in the branchcontrolled by the selection means.

10. The phase control apparatus as claimed in claim 8 wherein saiddigital control Words are in the binary radix and each said phasecontrol module further includes a hybrid coupler connected to the twophase shifters in each module.

11. Phase control apparatus for a system having a plurality of ports,

said apparatus being responsive to binary control words,

comprising a plurality of phase control modules arranged in a levelcorresponding to an order of said binary control words,

each said phase control module having two branches,

each said branch including a phase shifter which imparts a fixed andpredetermined amount of phase shift to a signal applied to that branchand selection means for connecting that branch in circuit,

the phase shifter in one branch of each module i-mparting a shiftradians different from the phase shifter in the corresponding branch ofthe immediately adjacent module in the same level and the phase shifterin the other branch of each module imparting a shift radians differentfrom the phase shifter in the corresponding branch of said immediatelyadjacent module, the shifts imparted by the phase shifters in said onebranches of the modules being in inverse relation to the phase shiftsimparted by the phase shifters in said another branches of the modules,

and means to actuate said phase shifter selection means in accordancewith the binary control words to connect each said port through acorresponding phase module so that said apparatus produces a uniformphase differential between said ports in said system.

12. A digitally responsive phase control system comprising a pluralityof phase control modules,

each said phase control module having an input, an

output, and N branches where N is the radix of digital control,

each said branch including a fixed phase shifter,

said phase shifters being arranged so that one set of correspondingbranches in said phase modules imposes a phase gradient on the signaltransmitted through said phase modules,

and another set of corresponding branches imposes a phase gradient of Kon the signal transmitted through said phase modules where K is aninteger, said one set imposing a phase gradient that is inverselyrelated to the phase gradient imposed by said another set,

and means responsive to digital control to connect all the phaseshifters in one set in circuit between said module inputs and saidmodule outputs in accordance with the value of the control to impose apredetermined phase gradient as a function of the control on the signaltransmitted through said modules.

13. A beam control system for an antenna array having a plurality ofantenna elements,

comprising a source of digital control words,

a multiplicity of phase control modules arranged in a plurality oflevels in a branching matrix,

each said level corresponding to an order of said'digital control words,power divider means connected between succeeding levels for couplingpower applied to said matrix between levels so that each antenna elementin said array responds to the same amount of power,

each said phase control module having N branches Where N is the radix ofsaid digital control Words,

each said branch including a phase shifter which imparts a fixed andpredetermined amount of phase shift to a signal applied to that branch,

the phase shifter in one branch of each module imparting a shift bradians different from the phase shifter in the corresponding branch ofthe immediately adjacent module in the same level and the phase shifterin another branch of each module imparting a shift K radians differentfrom the phase shifter in the corresponding branch of said immediatelyadjacent module, Where K is an integer,

and digital control word selection means coupled between said source andeach branch for connecting that branch in circuit so that each antennaelement is connected to a matrix terminal through a phase module in eachlevel with a uniform phase differential between said antenna elements insaid array being produced by said matrix.

14. The system as claimed in claim 13 wherein the modules in at leastone level are arranged in two groups and the selection means for eachgroup are independently controllable in response to said digital controlwords so that a tapered aperture illumination may be produced.

15. The beam control system as claimed in claim 13 wherein each levelincludes N times as many phase modules as the preceding level where N isthe radix of the digital control of that level.

16. The beam control system as claimed in claim 15 wherein each saidselection means includes two phase shifter isolating devices, onedisposed on either side of the phase shifter connected in the branchcontrolled by the selection means.

17. The apparatus as claimed in claim 15 wherein said power dividermeans includes a four port coupler associated with each module,

means connecting each input port to a corresponding phase shifter in theassociated module and means connecting each output port to a phasemodule in the succeeding level.

References Cited by the Examiner UNITED STATES PATENTS 3,056,961 10/1962 Mitchell. 3,069,629 12/1962 Wolff 3337 X 3,192,530 5/1965 Small343-854 CHESTER L. JUST'US, Primary Examiner.

H. C. WAMSLEY, Assistant Examiner.

12. A DIGITALLY RESPONSIVE PHASE CONTROL SYSTEM COMPRISING A PLURALITYOF PHASE CONTROL MODULES, EACH SAID PHASE CONTROL MODULE HAVING ANINPUT, AN OUTPUT, AND N BRANCHES WHERE N IS THE RADIX OF DIGITALCONTROL, EACH SAID BRANCH INCLUDING A FIXED PHASE SHIFTER, SAID PHASESHIFTERS BEING ARRANGED SO THAT ONE SET OF CORRESPONDING BRANCHES INSAID PHASE MODULES IMPOSES A PHASE GRADIENT 0 ON THE SIGNAL TRANSMITTEDTHROUGH SAID PHASE MODULES, AND ANOTHER SET OF CORRESPONDING BRANCHESIMPOSES A PHASE GRADIENT OF K0 ON THE DIGNAL TRANSMITTED THROUGH SAIDPHASE MODULES WHERE K IS AN INTERGER, SAID ONE SET IMPOSING A PHASEGRADIENT THAT IS INVERSELY RELATED TO THE PHASE GRADIENT IMPOSED BY SAIDANOTHER SET, AND MEANS RESPONSIVE TO DIGITAL CONTROL TO CONNECT ALL THEPHASE SHIFTERS IN ONE SET IN CIRCUIT BETWEEN SAID MODULE INPUTS AND SAIDMODULE OUTPUTS IN ACCORD-